The use of certain polymeric fibers, as opposed to primarily polyurethane foam, to make filled articles such as pads or cushions has been shown to result in improved performance characteristics. Compared with foam products, fiber-filled products may be more durable, have lighter weight, have greater permeability, be less costly, and be more readily recyclable.
A further improvement in the quality of fiber-filled articles was described in U.S. Pat. No. 4,940,502, wherein clusters of fibers, sometimes termed fiberballs, were used to create fiber-filled products. Fiberballs have a three dimensional structure which provides resilience upon deformation. From experiments reported in U.S. Pat. No. 5,169,580, fiberball cushions showed firmer support and higher resistance to repetitive compressions than batt cushions, even when the fiberball cushions were of a lower density. When molded, the forces which bond the fiberballs to each other are generally much weaker than the forces which resist compression of the individual fiberballs. This structure allows for resilience while also providing adequate local stiffness.
Although several patents, for example U.S. Pat. Nos. 5,169,580; 5,454,992; and 5,492,662, disclose processes and machinery for molding fiber-filled products, little attempt has been made to relate particular aspects of the molding method and apparatus to the performance and utility of the articles produced.